Shielded nuclear containment chambers, referred to as hot cells or isolators, are used in the radiopharmaceutical and nuclear energy industries to protect personnel from the radioactive material contained therein and radiation emitted therefrom. As used herein, hot cells and isolators are collectively referred to as isolators. In the radiopharmaceutical industry, radioactive material used for diagnostic and therapeutic purposes may be produced using a radionuclide generator, such as column housed in an isolator. Additionally, associated radionuclide process equipment is typically housed in an isolator.
Air filters such as HEPA filters are used to provide pharmaceutical grade sterile filtered air to isolators. Typically, one or more HEPA filters are mounted in the ceiling of the isolator. For instance, four HEPA filters may be used in a 2×2 matrix.
The integrity of each HEPA filter must be certified regularly by challenging the integrity of the full filter HEPA membrane surface, as well as any associated filter frame housing gaskets and/or seals (e.g. gel seals). Filter integrity testing is typically performed manually by introducing an aerosol such as dispersed oil particulate “DOP” or a poly alpha olefin (“PAO”) aerosol from the inlet filter plenum, and checking for leakage of this aerosol through the filter or housing at the filter outlet. Typically, an operator moves a hand-held scanning probe in overlapping strokes across every square inch of the HEPA filter face and seal, keeping the probe a maximum distance of about 2.5 cm from the filter face at all times, and moving no faster than about 3 meters per minute. The probe draws a continuous air sample during this scanning process that is monitored for presence of aerosol. If aerosol is detected, an alarm sounds and the operator stops and investigates.
Radionuclide isolator HEPA filter scanning by known methods may be problematic for a number of reasons. For instance, filter access is difficult within small isolators. Further, process equipment and/or processing sequence may block, impair or limit interior access. Further, delicate HEPA filter membrane may be damaged if a hand-held probe contacts the filter face during manual scanning. Yet further, manual movement rate and probe distance from the filter face is difficult to gauge and is inconsistent. Moreover, it is difficult to certify that sequential manual strokes overlap thereby assuring that the entire filter face has been scanned. Still further, the time required to test filter media may present unsafe radiation and/or hazardous chemical exposure conditions for the testing personnel. Yet further, isolators often utilize a diffusion grid or membrane situated between the HEPA filters and the isolator working volume in order to create a full ceiling HEPA filtered unidirectional airflow. Such diffusion grids or membranes must be manually removed in order to access HEPA filters and perform HEPA filter certification and then reinstalled after certification is complete. Manually handling diffusion grids or membranes can cause damage to filters and the grids/membranes, and thereby increase testing time and concomitant process cycle time. A need therefore exists for improved HEPA filter integrity testing systems and methods.
This Background section is intended to introduce the reader to various aspects of art that may be related to various embodiments and aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various embodiments and aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.